Telephone system



y 1940-v I J. DAVIDSON, JR

TELEPHONE SYSTEM 4 Sheets-Sheet 1 Filed Dec. 30, 1938 INVENTOR BYJDAV/DSON JR.

A T TORNE Y y 0- J. DAVIDSON, J-R

TELEPHONE SYSTEM 4 Sheets-Sheet 2 Filed Dec. 30, 1938 MON IN VE N TOR By .4011 V/DSON JR.

ATTORNE V July 23, 1940. bAvmsoN, JR

TELEPHONE SYSTEM Filed Dec. 30, 1938 4 Sheets-Sheet 3 IIHI- //v l/EN TORJ. DAVIDSON JR.

JILII o2 m bPi A T TORNE July 23, 1940..

J. DAVIDSON, JR

TELEPHONE SYSTEM Filed Dec. so, 1938 4 Shae ts-Sheet 4 lNl/ENTOR By J.DAVIDSON JR.

{L Gov A T TORNE V Patented July 23, 1940 UNITED STATES TELEPHONE SYSTEMJohn Davidson, Jr., Montclair, N. J., assignor to Bell TelephoneLaboratories, Incorporated, New York, N. Y., a corporation of New YorkJAN 6 Application December so, 1938, Serial No. 248,433

9 Claims.

This invention relates to telephone systems and particularly to specialservice systems such as intercepting equipments in telephone systems.

An object of the invention is to provide an improved economicallyarranged ringing, signaling and tripping arrangement for interceptingequipment.

Heretofore, automatic telephone systems have been provided in which whena subscribers line 10 is changed or disconnected, calls therefor areextended to terminals connectedto an intercepting trunk leading tointercepting apparatus for supervision by an operator. In such systemsin case of an intercepting trunk circuit, for example, extending to adistant omce, the ringing is usually tripped by the application of aground potential on one of the conductors to operate the usual trippingrelay. In my copending application, Serial No. 154,231 of July 17, 1937,special tripping arrangements have been shown including cold cathodetubes applied to a single party subscribers line system. With thiscathode tube arrangement a relay in the automatic system is operated totrip the ringing as soon as the con-, nection is established to theterminals of the intercepting trunk circuit.

It is a feature of the present invention to provide a circuitarrangement for intercepting calls intended for subscribers on partylines, and means is provided whereby when a party line is seized and theringing code ofthe party on said line, calls for whom are to beintercepted, is transmitted to said line, ringing is discontinued and anintercepting trunk which is associated with said line is connected forrecepton of the call. Cold cathode tubes are employed which areresponsive to particular ringing signals transmitted to the party linerepresenting the call for the party, calls for whom are to beintercepted.

A special feature is a delay means whereby the ringing is discontinuedbefore the trunk is me pared for the signaling of an intercepting operator to answer the call.

The invention has been illustrated in accompanying drawings in which:

Fig. 1 shows a calling subscriber's line, an intermediate switch indiagrammatic form and a connector and associated terminals of anautomatic .step-by-step telephone system arranged for applying ringingto a. ten-party line;

' Fig. 2 shows an intercepting trunk connected to said terminals andselectable by the connector shown in Fig. l for intercepting callsfor'any at particular party, calls for whom are to be intercepted, inaccordance with the applicants invention;

REISSUED Fig. 3 shows a connector and associated ter minals of anautomatic step-by-step system arranged ior ringing eight or four-partylines; Fig. 4 shows an intercepting trunk arrangement for intercepting acall for any one of the parties on a four or eight party line, calls forwhom are to be intercepted; and I Fig. 5 shows a modified portion of anintercepting trunk according to Fig. 2'or 4 with the special relay meansomitted.

Referring now to the drawings and particularly to Figs. 1 and 2,terminals I00 which are selectable by a connector C shown in Fig. l andnormally extend to a ten-party line have also been extended to anintercepting trunk shown in Fig. 2 so that calls for a particular one ofthe ten parties on this line will be intercepted by an operator. Thisintercepting trunk in Fig. 2 terminates in a jack 200 in front of anoperator's position who intercepts calls directed over this trunk.

If it is assumed that the last three digits of a called subscribersnumber which is the number of one of the parties on a ten-partyline andcalls for whom are to be intercepted, causes the brushes of connector Cto land on the terminals I00, and the connector to transmit the desiredcode signals, the operations of the connector may be as follows: Thefirst two of these three last digits locate the brushes of thisconnector on the terminals I00 and the third or last digit selects andtransmits the desired code. The connector may be seized by brushes IOIof a selector by connecting with the terminals of this connector when acall comes in from a calling subscriber such as I02 as is well known inthe art. This causes the relay I03 to operate over a circuit frombattery and ground through the windings of this relay, contact of relayI 04, terminals of the connector andthe brushes of selector IOI throughthe calling subscriber's loop. The operation of "relay I03 closes anobvious circuit for the operation of relay I05 which is slow inreleasing and remains operated during the pulses constituting succeedingdigits. The operation of relay I05 closes a circuit for a relay I06 frombattery, lower winding of this relay, the vertical oiT-normal contactsI0I, contacts of relay I05 to ground. The first releaseof the pulsingrelay I03 when the calling subscriber dials the first of these threedigits now closes a circuit for the vertical magnet I08 from battery,winding of this magnet, contacts of relays I 06 I09, I05 and I 03 toground. This causes the connector to take one vertical step and open thevertical off-normal contacts I01. This opens the above-mentioned circuitfor relay I06 but this relay remains operated as it is slow in releasingand holds over a circuit from battery through its upper Winding andupper armature and front contact through the above-mentioned pulsingcircuit and is consequently maintained operated during the pulsing ofthe digit. When this digit has been sent, the final operation of thepulsing relay I03 opens the holding circuit for relay I06 which nowreleases. On the first release of the pulsing relay I03 in response tothe second digit, a circuit is closed for the rotary magnet H0 and therelay III. The circuit for magnet H0 extends from battery through thewinding of this magnet, contacts of relays H2, I06, I09, I05 and I03 toground and the circuit for relay III extends from battery through thewinding of this relay over the same pulsing circuit. Relay III is slowin releasing and is held operated by a holding circuit over its lowerarmature and front contact through the pulsing circuit-during thepulsing of this digit. At the end of this second series of impulses, thebrushes of the connector have been advanced to and connected with theterminals I00 of the desired party line.

Relay III then releases if,the party line is idle. However, if thisparty line is busy, relay III remains operated long enough to permit theoperation of relay I09 over a circuit from battery through the windingof this relay, contacts of relay I II to ground'on the sleeve terminalsat I00 and'when relay III is released, relay [I09 is locked overmake-before-breakcontacts of relay III to ground over its lower innerarmature and,

front contact and contacts of relay I05. A busy tone is therebytransmitted to the calling subscriber indicating that the line is busy.This tone circuit is extended from the busy tone source at I I4, acondenser I I5, contacts of relays II2 andl09, a condenser I I6 over thetip conductor to the calling subscriber's telephone. If, however, thecalled party line is ,idle relay H2 is operated when relay III releasesover a circuit from battery through a resistance and contacts of relay20I in Fig. 2 over the sleeve terminal and brush of the connector,contacts of relay I I I, upper winding of relay H2, contacts of relays I09 and I05 to ground. Relay H2 locks through a circuit from battery, itslower winding and second lower armature and front contact to ground atcontacts of relay I 05. Relay H2 also closes a circuit for the operationof" the rotary magnet I I8 for the operation of the code selectingrotary type step-by-step switch I20. The first release of the pulserelay I03 in response to the third digit now closes a circuit for theoperation of this magnet as follows: From battery through the winding ofmagnet H8, contacts of relays H2, I06, I09, I05 and I03. It should benoted that relay III is also operated in'this circuit as hereinbeforetraced. Relay III remains operated during the sending of the pulses ofthis last digit. The rotary magnet II 8 advances the brushes I2I and I22over the associated contact banks of the switch I20 to select thedesired ringing code. The impulses for selecting a ringing code may, asthis is a ten-party selective code ringing system, consist of from oneto ten impulses. The brushes of this switch therefore will land on anyone of the ten terminals as shown in the drawings and connect any one ofthe five generators indicated I to!) to the corresponding over the tipconductor.

terminals and brushes to leads connected to contacts of relay I25, thepurpose of which will be described hereinafter. III, when the codeselecting digit has been sent, the original energizing circuit for relayH2 is opened, but this relay H2 remains locked as described. When relayH2 was operated and while relay III remained operated, a circuit wascompleted for the operation of relay I09 from battery through thewinding of this relay, contacts of relays III and H2- to ground. Thisground also serves to make the line busy as it is connected to thesleeve lead. On the release of relay III, relay I09 locks-over themake-beforebreak contact of relay III to a ground at relay I05. RelayIII in releasing closes a circuit for relay I25 from battery, winding ofthis relay, contacts of relay I21, make-before-break contacts of relayI25, contacts of relays III, I09 and I I2 to ground. The connector isnow ready for the transmission of the selected code to the interceptingtrunk as shown in Fig. 2.

It should be noted that the trunk in Fig. 2 is provided with a key 202.This may be operated to connect a cold cathode tube 203 to the tip orthe ring conductor of this intercepting trunk, depending on whether ornot the called party, calls for whom are to be intercepted, is to berung on the tip or the ring conductor by a code. If it isassumed thatthe key 202 is operatedto connect tube 203 to the tip conductor, thecall for the intercepted party is assumed to be transmitted It shouldalso be noted that lead 204 may be connected to any one of the group offive leads 205 which are connected On the release of relay to fivegenerators not shown but identified by legends generator I to generator5 and to the first five terminals of the twobanks. of switch I20. Thelead 204 is therefore connected to one of these five leads depending onthe code of the party for whom calls are to be intercepted and if it isassumed that it is connected to the first conductor which extends to thegenerator No. I and the first contact onthe banks the number dialed bythe calling subscriber would be 1. The brushes I2I and I22 of the switchI20 would therefore be connected to the first terminals of theirrespective banks. On the operation of relay I25,-the generator I willtherefore now transmit codeNo. 1 over the first terminal of the upperbank through the brush to the lead connected to the second upperarmature and front contact of relay I25, upper armature and back contactof relay I2'I, upper inner armature and front contact of relay II2 overthe tip conductor through key 202 through the tube I03 to ground. Thiscauses the firing of the tube 203 and a circuit is completed over themain anode of this tube from ground through the winding of relay 206,back over the tip conductor to the generator I. This causes theoperation of relay 206 which now closes a circuit through the upperarmature and front contact from the generator I over the tip connectionthrough the upper electrode 201 of the tube 208 and establishes acertainpotential on this electrode. It should be noted also that the samepotential from the same generator I is supplied on the lower electrode209 of the tube 208 by the operation of relay 206 from generator I overthe first conductor of the group 205, conductor 204, second lowerarmature and front contact of relay 206 to the electrode 209.Consequently, tube 200 will not become active as these potentials are ofthe same value. This matching of the applied potentials on the twoelectrodes of the tube 200 identities the code ringing for the party,calls for whom areto be intercepted, so that the trunk will be preparedior the intercepting of this call as will be further explained as thedescription proceeds. Associated with the generators I to is a pick-upinterrupter I which operates to connect ground to the pick-up lead I 3|,once between each transmission of the code by said generators so thatwhen a code has been transmitted as described to the tube 208 and iscompleted, ground will be connected to conductor Iti' from the pick-upinterrupter I20 for theoperation of relay 2I0. Relay 2I0 in operatingapplies a ground for the operation of the delay circuit comprising therelays 2, ground applied by relay 2I0causes the operation of relay Hifrom battery through the winding of this relay and its make-before-breakcontacts, contacts of relays m, 20.8 and 2I0 to ground. This ground alsocloses a circuit for the operation of the relay 20I from battery throughthe winding of this relay and its makebefore-break contacts, contacts ofrelays 2L5, 206 and 2M] to ground. Relay 2M looks over its middle lowerarmature and front contact to the ground on the sleeve conductor appliedat relay H2 and relay 2II.locks over its armature and conductor.

front contact, contacts of relay 20I to ground on the sleeve at relay II2. Relay H2 is prevented from operating at this time as long as theground is supplied from the contacts of relay 2I0 as it isshort-circuited by this ground at its upper outer armature and backcontact. However, as soon as relay 2I0 releases relay 2I2 is operatedover a circuit from battery winding of relay2i2, contacts of relays 2II,2M, II2 to ground over the sleeve. The tripping of the ringing code isaccomplished as soon as relay 2M is operated as the tip and ringconductors are connected through the contacts of this relay to the twoelectrodes oi, the cold cathode tube 223 which therefore shunts the tipand ring conductorsand causes the operation of relay I21 over a circuitextending from battery through the upper winding of relay I21, contactsof this relay, contacts of relay I25, the first contacts on the lowerbank, brush I2I and contacts of relays I25, I27, H2 over the ringconductor, contacts of relay 20I, through tube 223, contacts of relay20I over the ,tip conductor, contacts of relays H2, I21, I25,

reverses the battery and ground through the I windings of relay I03 forsupervision. Then when the pick-up ground is again extended from pick-upinterrupter I30 over lead I3I relay 2I3 operates from battery winding ofrelay 2I3 and its make-before-break contacts, contacts of relay 2I2,conductor I3I, pick-up interrupter I30 .to ground. Relay 2I3 looks overits upper armature and front contacts through contacts of relays 20I andH2 to ground over the sleeve Relay 2I3 in operating closes a circuit forrelay 2I8, and this relay in turn closes an obvious circuit for lightingof lamp-220 to indicate to the operator that a call has been interceptedon this trunk. The purpose of this delay 2l2 and 2I3. At this time,thiscircuit is therefore to permit the tripping of the ringing beforethe lamp 220 is operated and the operator has a chance toinsert the plug22I into jack 200. When the operator answers the call by inserting plug22I into Jack 200, relay 222 operates and extinguishes lamp 220.Transmission battery for talking is now supplied for the callingsubscriber through the winding of relay I03 and for the operator throughthe winding of relay I 04. Conversation between the subscriber andoperator may now begin.

If the calling subscriber disconnects first, relay the connector switchand the release magnet II for the ringing code selecting switch I20. Thecircuit for the release magnet I40 may extend from battery through thewinding of this magnet, the vertical oilE-nonnal contacts I02, contactsof relays I05 and I04 to ground and the circuit for the release magnet IM for switch I20 exends from battery through the winding of this magnet,off-normal contacts I43 of the switch I20, contacts of relays I05 andI00 to ground. When these two switches are returned to normal, thecircuit for the two release magnets are opened. The release of relay II2disconnects the ground on the sleeve causing the release of relays 20L2, M2, 2I3 and tilt. In case the operator. disconnects first, the relayI00 releases and reverses the battery over the tip 'and ring conductorsto the preceding switches and when the calling subscriber disconnects,relay I03'is released causing the release of relays I 09, I21

and II2 and the release of the switches as described.

300 of afour-party or eight-party line for the interception of callsincoming to any one of the parties of these two types of lines; Theconnector CI is similar to the connector C in Fig. l and operatespractically in the identical manner as far as selecting a party line isconcerned. The operations of this connector as far as the functionsthereof in making the selection of a party line are concerned need nottherefore be described in detail. It may consequently be assumed thatthe connector functions have progressed to the point where relay 30I hasbeen operated. This relay corresponds to relay I 25 in connector C andthe description may therefore begin with the transmission of the thirdor ringing codeselecting digit. It should be noted that in Fig. 4, a key400 may be operated to connect either the tip or the ring to the tube402 for the reception of the code signal over the tip or the ringconductor. Ringing code selecting switch 303 is in; case of a four-partyline, of

course, only equipped for four selections by the operation of the switch303 from oneto four steps, and in the case of an eight-party lineequipped as shown for eight selections. The selections of a code asdetermined by the setting of this. switch will always cause theoperation of relay 305 over a circuit from, battery, winding of thisrelay, contacts of relay 3M and through the brush 300 and any terminalof the associated bank to the corresponding interrupter l M2 tointerrupt the operation-of this relay in accordance with theinterruptions as determined by interrupter I for the first four steps orin accordance with the interruptions as determined by interrupter 2 forthe last four steps to transmit superimposed ringing current over a tipor ring conductor as determined by the operation of relay 301 or 308 orboth of these relays or neither of these two relays. If it is assumedthat the switch 303 has been set to apply a code for the first party onany type of party line, the brush 310 will land on the first. terminalof the associated bank and thus neither of the relays 301 or 308 will beoperated. In this case superimposed negative current will be applied onthe tip conductor and interrupted in accordance with the interruptionsof relay 305 as determined by the interrupter 1 controlled by the brush306 of the switch 303. In this case the negative superimposed currentwill be supplied at a source connected at 312, and the circuit may betraced from this source over contacts of relays 305 and 301, upperwinding of relay 315, contacts of re-' lays 301, 308, 315 and 310, thetip conductor, key 400, key 403, the upper electrode of tube 402, thelower electrode of this tube, key 403 to ground. This causes the firingof tube 402 which thereby closes a circuit over its main anode throughthe upper winding of relay 404 causing this relay to operate and lookthrough its lower winding to ground at contacts of relay 405. When thecode has been transmitted once, the usual pick-up interrupter 319 willsupply ground on the lead 406 causing relay 405 to operate and thisrelay in turn applies ground through contacts of relays 404 and 408,winding of this relay to battery causing relay 408 to operate and lookover its middle lower armature and front contact over the sleeveconductor to ground at relay 316. This ground on pick-up conductor 406also causes the operation of the first delay circuit relay 410 frombattery through the winding of this relay and its make-before-breakcontacts, contacts of relays 404 and 405' to ground. When the ground onthe pick-up interrupter 319 is removed, the delay circuit relay 411 willoperate from battery.

through the winding of this relay, contacts of relays 410 and 408, overthe sleeve conductor to ground at relay 316. When relay 408 operates itconnects the tip and ring conductors to the cold cathode tube 413 whichthen is broken down by the ringing current and closes a circuit for theoperation of relay 315 from .the negative tripping battery at 318through contacts of relay 305 when it is released, contacts of relay301, upper winding of. relay 315, contacts of relays 301, 308 and 315over the tip conductor, contacts of relay 408 through tube 413, contactsof relay 408, back over the ring conductor, contacts of relays 316, 315and 308 to the generator ground at 318. Relay 315 locks through itslower winding from battery, its second lower armature and front contactin the ground at relay 320. Relay 315 opens the circuit for relay 301which new releases causing the release of relay 305, causing the ringingcode to be discontinued. On the next connection of ground through thepick-up interrupter 3| 9 a circuit is completed for the last delaycircuit 418 from battery through the winding of this relay,make-before-break contacts of this relay, contact of relay 411 to theground at the pick-up interrupter 318. Relay 418 closes a circuit forrelay 420 which new lights lamp 421 to indicate to the operator that acall is Similarly any other code'may be supplied over the tip or ringconductors by the settings of the code ringing selecting switch 303 andthe consequent operations of relays 301 and 308 and variouscombinations. For example, if the switches select the secon ct'contacton the banks, relay 308 is operated from battery through the lowerwinding of this relay over the second contact through brush 310,contacts of relay 301 to ground. This closes a circuit for thetransmission of superimposed negative ringing current over the ringconductor from the source 312, contacts of relays 305, 301, upperwinding of relay 315, contacts of relays 301, 308 and 315 over the ringconductor. If the brushes of the crossselector are advanced to the thirdcontact, relay 301 is operated from battery, through the upper windingof this relay, third contact and brush 3E0 to ground at relay 301. Inthis case superimposed positive ringing current will be transmitted overthe tip conductor from the source at 323, contacts of relays 301, 305,301, upper winding 01 315, contacts of relays 301, 308, 315 and over thetip conductors. If the fourth contacts are selected, both relays 301 and308 are operated and superimposed positive ringing current istransmitted over ring conductor. The circuit for relays 301 and,308 maybe traced from battery through the lower winding of relay 301, upperwinding of relay 308, the fourth contact and brush 310 to ground atcontacts of relay 301,

and the circuit for the ringing current may be from the source 323,contacts of relays 301, 305, 301, upper winding of relay 315, contactsof relays 301, 308, 315 over the ring conductor. Similarly if the switch303 is set to the fifth, sixth, seventh and eighth contacts, the sametype 01 ringing current is transmitted from the sources 312 and 323 overthe corresponding conductors as for codes 1, 2, 3 and 4. but relay 305will be interrupted at a different rate as the brush 308 will connectwith the interrupter 2 in its various positions 5, 6, 1 and 8. I

If Fig. 5 is inserted between the positions A and B as shown indash-dotted lines in Fig. 2 or. Fig. 4. it is evident from this figurethat the delay circuit for operating the signal 220 or 421 is omitted sothat when relay 201 or 408 is operated, the ringing is tripped throughthetube 500 and at the same time, relay 501 is operated by the ringingcurrent. This relay is locked to ground on the sleeve circuit. Relay 501closes an obvious circuit for the operation of relay 218 or 420 whichoperates thesignal 220 or 421. This arrangement may be used where it isnot desired to have any delay in operating the signals.

What is claimed is:

1. In a telephone system, a calling line. a called party line, means forestablishing a connection from said calling line to said called line andfor transmitting a ringing code to said party line for calling any oneof the parties on said line, an intercepting trunk associated with saidcalled party line, and means responsive to a particular ringing codetransmitted to said party line and trunk for establishing a talkingconnection over said trunk.

2. In a telephone system, a calling line, a

called party line, means for establishing a connection from said callingline to said called line and for transmitting ringing code to said partyline for calling any one of the parties on said line, an interceptingtrunk associated with said called party line, and means responsive to aparticular ringing code transmitted to said party line and said trunkfor establishing a talking connection over said trunk and fordisconnecting said code ringing;

3. In a telephone system, a calling line, a called party line, anintercepting trunk, associated with said called party line, an'operatorsposition, means for establishing a connection from said calling linetosaid called party line and to said intercepting trunk for transmittingringing codes to said party line and trunk, and

means for establishing a talking connection from said calling line oversaid intercepting trunk to said operator's position operative if aparticular ringing code is transmitted.

4. In a telephone system, a calling line, a called party line,an'operator's position, an. intercepting trunk associated with saidcalled party line, means for establishing a connection from said callingline to said called line and for transmitting a ringing code to saidparty line for calling any one of the parties on said line, and means insaid trunk for discontinuing the transmission of aparticular ringingcurrent to said party line and for establishing a connection over saidintercepting trunk to said operators position. I

5. In a telephone system, a calling line, a called party line, anintercepting trunk, associated with said calledparty line, an operatorsposition, means for establishing a connection from the calling line tosaid called line and said trunk and for transmitting diflerent ringingcodes to call corresponding parties on said party lines, meansresponsive to'the transmission of a particular ringing code fordiscontinuing said transmission and for establishing a certain intervalthereafter a talking connection from the calling line to said operator'sposition over said trunk.

6. In a telephone system, a calling line, 8.

called party line, an intercepting trunk associated with said calledparty line andterminating at said operator's position, an operator'sposition, a signal at said operator's position, means for establishing aconnection from the callin line to said called party line and said trunkand 1 for transmitting diflerent ringing codes to call ticular ringingcode for discontinuing said transmission and for operating said signal.

,7. In a telephone system, a calling line, 9. called party line, anintercepting trunk, an operators position, a signal, means forestablishing a connection from the calling line to said called partyline and said trunk and fortransmitting diflerent ringing codes to callcorresponding parties on said party lines, and means responsive to thetransmission'oi a particular ringing code for discontinuing saidtransmission and for operating said ,signal a certain time intervalthereafter.

8. In a telephone system, a calling line, a called party line, means forestablishing a connection from said calling line to said called partyline in response to dial pulses, means for selecting a particular"ringing code for ringing a corresponding party on said called partyline in response to dial pulses and for transmitting said ringing codeat intervals to said called party line, means for producing a signalduring the interval between the transmission of said ringing code, anintercepting trunk connected to said called line having a normallyopened talking connection, means associated with said intercepting trunkoperative in response to the transmission corresponding parties on saidparty lines and ringing code at intervals to said called party line,

means for producing a signal during the interval between thetransmission of said ringing code, an intercepting trunk connected tosaid called line having. a normally opened talking connection, meansassociated with said intercepting in'unk operative in response to thetransmission oi! said particular ringing code to said called party lineand to said intermediate signal for closing said talking connection andfor thereafter discontinuing the transmission 0! ringing code and theintermediate signal, a signaling device, means operative in response tosaid first-mentioned signal tor actuating said signaling device adefinite interval after said ringing code has been discontinued.

' JOHN DAVIDSON. Ja.

